public class MyElement : FrameworkElement
{
   // .........
}

var myElement = new MyElement {Focusable = true, IsEnabled = true};
var a = myElement.Focus();
var b = Keyboard.Focus(myElement);

public class MyElement : FrameworkElement
{
    public static readonly DependencyProperty IsTabStopProperty;
    public static readonly DependencyProperty TabIndexProperty;


    static Cell()
    {
        IsTabStopProperty = KeyboardNavigation.IsTabStopProperty.AddOwner(typeof(Cell));
        TabIndexProperty = KeyboardNavigation.TabIndexProperty.AddOwner(typeof(Cell));

    }

    public bool IsTabStop
    {
        get
        {
            return (bool)base.GetValue(IsTabStopProperty);
        }
        set
        {
            base.SetValue(IsTabStopProperty, value);
        }
    }

    public int TabIndex
    {
        get
        {
            return (int)base.GetValue(TabIndexProperty);
        }
        set
        {
            base.SetValue(TabIndexProperty, value);
        }
    }
   
    // .............
}

 Panel panel = this.Parent as Panel;
 FocusManager.SetFocusedElement(panel, this);

А> Panel panel = this.Parent as Panel;
А> FocusManager.SetFocusedElement(panel, this);
А>

 FocusManager.SetIsFocusScope(this, true);

Deriving from the Control class is the model used by most of the existing WPF controls
...
Consider deriving from FrameworkElement if any of the following apply:

— You want to have precise control over the appearance of your control beyond what is provided by simple element composition.
— You want to define the appearance of your control by defining your own render logic.
— You want to compose existing elements in novel ways that go beyond what is possible with UserControl and Control.

// Да-да, абсолютно пустой класс
public class MyElement : FrameworkElement
{
}

...
private void SomeMethodOfWindow()
{
    var myElement = new MyElement { Focusable = true, IsEnabled = true, Width = 50, Height = 50 };
    grid.Children.Add(myElement);
}

DMS>>>Что за бред Имелось ввиду уровне [абстракции]. "Знание предмета на низком уровне" оставляем в пэтэушном прошлом

DMS>>> типичная поза программиста — фиг с ним, пусть не работает, но зато мощно и расширяемO

If you intend to use FrameworkElement as a base class, you might want to first examine the existing derived classes. FrameworkElement provides support for a number of basic scenarios, but also lacks a number of features that are desirable for an "element" in the sense of a building block that you use to create user interface (UI) in Extensible Application Markup Language (XAML). For instance, a FrameworkElement does not define any true content model; FrameworkElement as a base class does not define a property that can create XAML child elements. In particular, you might want to look at Control and ContentControl.